Unforgivable
by allonsyforever
Summary: My take on what happened when Sirius decided to play a prank on Snivellus, and how it affected the Marauders for years afterward. Mentions James/Lily, Snape/Lily, some Sirius/Remus.


Double Potions with the Slytherins was something quite dreaded by nearly all of the Gryffindors, but on this particular Wednesday afternoon, it turned out to be something of a surprisingly pleasant experience for a rather mischievous Sirius Black.

Hastily adding snails to his potion so that it bubbled indigo blue, just as Professor Slughorn glanced up, Sirius carelessly stirred the potion so that it became, unlike anyone else's, exactly how it should have looked when completed, and turned his attentions to far more important things, like Lupin. Moony, he thought, looked rather down.

James seemed to have been thinking along the same lines, for as he stirred his green potion in his cauldron he said quietly, as that the Slytherins at the next table did not overhear, "Moony, my friend, is it that time already? I hadn't been keeping good track." His eyes flickered to the spot where red-haired Lily Evans sat, leaving no doubt as to where exactly his thoughts had been wandering when he was not looking up at the moon.

"When?" asked Sirius. "Tonight?"

"Tomorrow," said Lupin curtly.

"Excellent," said Sirius with excitement gleaming in his eyes.

"You don't have to come, you know," murmured Lupin as he poured in his carefully measured roots.

"Don't be a prat, of course we do, we want to," said Sirius. "It's all good fun."

"It's all a great risk, that's what it is," said Lupin.

"Ah, what's life without a bit of risk?" grinned Padfoot.

"Safe?" Lupin muttered under his breath, glancing around and noticing Severus Snape staring towards them. Snape, upon being caught, looked quickly away at his potion, which, like Padfoot's, was done to perfection.

Sirius tossed his head casually, throwing his long hair out of his eyes, and followed his friend's gaze. His eyes flashed upon seeing Snape. "Hey, Snivellus," he said softly, ignoring Lupin's glare. "Stop being such a nosy git, will you?"

Snape's eyes turned upon them, dark and bright and dangerous. "Black, when you have the courage to confront me without your bloody friends surrounding you, let me know and we'll have a proper duel," he said icily, one hand lazily stirring the potion. "Until then… do yourself a favor, and shut up."

"_I'm _the one with no courage? Who's been spying on us?"

"I do not spy, Black, nor have I ever –"

"Don't lie, Snivellus!" sneered Sirius, raising his voice slightly, and several students looked around with interest. "You've been watching us for ages," he hissed.

"I have not –"

"Boys, boys, settle down now, settle down," Professor Slughorn bustled over to the marauder's table and glanced at each of their potions. "Black, watch it –" for Padfoot's potion had turned black and begun to bubble over the side of the cauldron; in his anger he had stirred it quite a bit too much. "Still, I saw that you had it right before, well done… shame you weren't in my House, boy, all your family… still…" and here Sirius glared at Slughorn while Snape smirked, "Potter, Lupin, full marks as usual, excellent work, boys, excellent – Pettigrew…" he looked at Wormtail's sickly green mixture, "leaves a little to be desired, but all the same… the effort that counts, I suppose, isn't it? Ah, and Severus, let's see here… full marks, well done…"

"Sir? I just had a question about a potion I heard about…" Moony stood and followed the Potions master to his desk. When Slughorn was out of earshot, Sirius began on Snape again. He glanced at James first, who nodded him on but did not join in the fun, for he had just noticed that across the room Lily Evans was frowning at them. He nervously flattened his black hair.

"What is it that you want, Snape?" asked Sirius scathingly. "To know how to fix your hair? 'Fraid we can't help you there, it seems rather hopeless –" James snorted despite himself "-or do you just like following us around? Wish you knew what it was like to actually have friends?"

Snape's eyes flashed as he turned on Sirius; James resisted the urge to pull his friend out of harm's way, keeping his eyes carefully trained on Snape's wand hand, which kept twitching towards his pocket. He knew Snivellus would not hesitate if he had the chance to hex any of them.

"Actually," said Severus quietly, his curiosity getting the better of him, "I wondered where exactly it is you four –" His cold gaze flicked to the others, one by one –"disappear to every few weeks, when you leave the castle."

"Keep your nose out of other peoples' business, Snape," said James quickly in an attempt to shut Sirius up before he went too far, "really, they'll start to think it's _you _who's up to something."

"So, Potter, you'll admit that you do vanish every now and again?"

"He didn't say that," Sirius said harshly, before James could reply. "He just told you to keep your nose – which, I might add, is exceptionally large –"

James smirked despite the look Lily Evans was giving him; Snape's wand flew out of his pocket, Sirius's did as well and within seconds the situation had gone from distasteful bickering to downright hatred between the three, or more specifically the two; James had pulled his wand out in case he needed to defend Sirius.

Snape's wand pointed at Sirius's heart and Sirius's, at Snape's head; as top students in the grade not only were they capable of sending one another to the hospital wing for a few days, they were also perfectly willing to do these things without much good reason, and they both knew it…

Several alarmed students had been watching the situation unfold, and now whispers flew around the classroom, bets were exchanged, laughter, even, rang out. James and Lily alone looked truly concerned. Remus was still up at Slughorn's desk.

"Snivellus," said Sirius in a deadly voice, "_Sev._ You want to know where we disappear to, once a month? You want to know? You really want to know?"

Snape said nothing; his mouth was a fine, furious line and his eyes darkened with hatred, but behind that, a burning curiosity lingered…

"The Whomping Willow," said Sirius, backing off a bit now that he had not been cursed simply for having the nerve to speak, and leaning up against the desk in that casual way only Sirius could (a girl behind him sighed), "At the full moon. Go right up to it. Duck underneath. And-" he made a motion with his hand –"poke it with a stick." Those nearby who had overheard laughed. James, however, did not. Down the table, Wormtail seemed not to have overheard, busy trying to get his yellow potion to turn blue. Moony had only just returned to the table. "And see what happens," said Sirius mildly as he and Snape both lowered their wands, still caught in a hateful stare.

"Black –" Snape looked around, but many of the students had now lost interest upon seeing that Sirius was clearly just joking around, "I will find out – if it's anything illegal-"

"Snivellus," said Sirius abruptly just to stop him talking, then he shook his head. "Oh, Snivellus, if only you knew_._"

He turned back to his friends, who did not look as amused as he thought they would.

Remus stayed behind in class to discuss something with Professor Slughorn, so James was the one who turned on Sirius as soon as they left the classroom.

He pulled him aside on their way to Transfiguration, into an empty classroom.

"What're you playing at?" he said to him seriously. "Are you mad?"

"Come off it, James," said Padfoot easily. "He didn't take it seriously, he thought I was joking like everyone else, didn't he? You saw the look on his face."

"I saw you tell him exactly where we go every month, and I saw Moony nearly faint."

"Don't you see, James?" asked Sirius, still looking amused. "The only thing to tell him was the truth – he'd never believe us anyway."

"Sirius, I don't know," said James uncomfortably, running a hand through his disheveled hair. "What if he does go? What if he sees…?"

"He won't go," said Sirius to his best friend, although he looked slightly less confident now. "He can't have thought I was serious. Even Snivellus isn't that thick…"

"Let's hope not," said James, and led the way back to the crowded corridor.

James did not speak to Sirius throughout the entire Transfiguration lesson, during which they were trying to turn hedgehogs into pincushions. Even Sirius did not complete the task, looking rather distracted, and they returned to the Gryffindor common room, a bit subdued.

"C'mon," said Sirius as soon as they walked in. "Listen, I was joking –" he grinned despite himself – "c'mon, you know I was joking – he's not really going to go duck under the Whomping Willow, no one's crazy enough to –"

"Shush," said James suddenly, and they all knew why as soon as they saw Lily sitting alone, curled into a chair by the fire and reading _Unfogging the Future_. She looked up when she saw they were there, did not return James's smile, made a noise of dissent in the back of her throat, and promptly exited the room with her book tucked under her arm.

Sirius put a hand on his arm. "Someday, mate," he said hopefully.

"You don't think she overheard, do you?" asked James anxiously.

"No! You worry too much. You do!" Sirius looked at him, the spirit of a good dose of risk lighting up his handsome face. "Look, Moony's furry little problem isn't going anywhere; we've got to go down there tomorrow night anyway and there's nothing you can do about it. Stop worrying; have a bit of fun. Exploding Snap?" he held out a deck of cards, and, after a moment, James nodded, and the two began a rather spectacular game.

The following afternoon, Lupin looked downright pale in Herbology and as they trooped back up to the castle with the Hufflepuffs he muttered, "Think I'll head to the hospital wing for a bit," rather miserably, and left them to go to Charms alone.

James, Sirius, and Peter exchanged looks. "We'll go down just after Charms, right?" muttered James, and they nodded.

However, they had to get some other things done before they could go out; dusk was fast approaching by the time they left their Charms lesson and headed back to their dormitory. James pulled out his Invisibility Cloak and looked down at the Marauder's Map –

A tiny dot labeled _Severus Snape_ was making its way down the grounds, headed straight for –

"Bloody hell," whispered James, his face going white, and before the others could ask, he was off, sprinting down the stairs and knocking people aside, ignoring their yells and dashing out of the common room. Down the stairs, into the front hall, and out of the front doors James tore, running faster than he ever had before – Sirius, surely, would not care when he saw Severus down there – in fact, he could picture his laugh clearly in his mind when he saw the Map – but Snape had been fast approaching the tunnel – and once he was inside –

James, Prongs, longed to transform as he sprinted across the darkening grounds; he could gallop as a stag much more quickly than he could run as a boy, but he knew Snape was going to see him. He just saw the Willow shake back to life as the tunnel closed shut. "No!" he yelled, running straight to the violent tree. The full moon was clearly in the sky…

One of the branches caught him across the shoulder but with the quick skills of a Seeker, he managed to break through and touch one finger the knot on the tree; it stopped moving immediately. He lowered himself into the tunnel, now yelling as he jogged along at a crouch, out of breath and heart racing – Lupin must have transformed already –

"SEVERUS!" he shouted, hearing his own voice echo. "SEVERUS –" And he nearly ran into him as he raced around another corner; he instinctively grabbed Snape around the shoulders and pulled him back – "Severus, get out of here –" he threw him behind him, he could see the wolfish form of Remus crouching in the doorway to the Shrieking Shack.

"Run, go on, get out of here!" James shouted, pushing him along, and finally Snape seemed to get the message and moved.

Once they were out, James panting slightly, Snape turned on him, face paler than any ghost, dark eyes gleaming.

"He's a werewolf?" he said, more than asked, for he had just seen very convincing evidence. "You're hiding a _werewolf_?"

James saw a rat vanish into the trees, and he had a sneaking suspicion that if he looked closely into the shadows he might see a large black dog staring back at him. His heart was still thumping, unnaturally loud in the dark silence of the night.

"Not hiding, exactly," said James, "but yes, he's a werewolf. You mustn't tell anyone, Severus. No one knows, except the four – well, now the five – of us and Dumbledore, and the teachers, of course."

"They _know_…?" said Snape incredulously. "He's a …"

"_Your word_, Severus, that you won't tell anyone? I did just save your life," said James, realizing this just as he spoke the words. "You sort of owe me one."

Snape's eyes were dark as he spoke, and deadly. "My word, _James_, that I will not tell a soul," he said in his icy, soft, snakelike voice. "However, as for you saving my life – I have no doubt that you were also saving your own skin, for in the event that I had died, you surely would have been to blame. Very funny joke," he sneered, although still clearly shaken, and with that, turned on his heel and strode back up to the castle.


End file.
